The invention relates to a process for preparing a mixed metal catalyst composition comprising bulk catalyst particles comprising at least one Group VIII non-noble metal and at least two Group VIB metals.
In the hydroprocessing of hydrocarbon feedstocks, the feedstocks are hydrotreated and/or hydrocracked in the presence of hydrogen. Hydroprocessing encompasses all processes in which a hydrocarbon feed is reacted with hydrogen at elevated temperature and elevated pressure including processes such as hydrogenation, hydrodesulfurization, hydrodenitrogenation, hydrodemetallization, hydrodearomatization, hydroisomerization, hydrodewaxing, hydrocracking, and hydrocracking under mild pressure conditions, which is commonly referred to as mild hydrocracking.
In general, hydroprocessing catalysts are composed of a carrier with a Group VIB metal component and a Group VIII non-noble metal component deposited thereon. Generally, such catalysts are prepared by impregnating a carrier with aqueous solutions of compounds of the metals in question, followed by one or more drying and calcination steps. Such a catalyst preparation process is described, e.g., in U.S. Pat. No. 2,873,257 and EP 0469675.
An alternative technique for the preparation of the above catalysts is described in U.S. Pat. No. 4,113,605, where, e.g., nickel carbonate is reacted with, e.g., MoO3 to form crystalline nickel molybdate, which is subsequently mixed and extruded with alumina.
A similar process is disclosed in DE 3029266, where nickel carbonate is mixed with WO3 and the resulting composition is mixed with alumina impregnated with, e.g., nickel nitrate and ammonium tungstate.
As the carrier itself has no or little catalytic activity, the activity of the above carrier-containing catalysts in hydroprocessing is rather moderate. It is therefore an object of the present invention to provide a catalyst which can be applied without a carrier. Such carrier-free catalysts are generally referred to as bulk catalysts.
The preparation of bulk catalysts is known, e.g., from GB 836,936 and EP 0014218. The catalyst of, e.g., EP 0014218 is prepared by spray-drying an aqueous slurry of potassium carbonate, potassium dichromate, vanadium oxide, iron oxide, portland cement, methyl cellulose, and graphite.
It is noted that all the above catalysts comprise one Group VIII non-noble metal and one Group VIB metal. Such catalysts have only moderate activity in hydroprocessing. It is therefore an object of the present invention to provide catalysts with increased catalytic activity.
GB 1 282 950 (D1) describes a process for manufacturing transparent gels containing iron and molybdenum and the uses thereof. The gels are prepared by a process in which the starting materials are mixed in the presence of a quantity of water not greater than that required to form individual saturated solutions of the compounds. Depending on the ratio between the reactants, the reaction mixture transfers to either a clear solution with a low viscosity or a more viscous solution containing a few undissolved crystals. What happens in the process of this reference is that the reactants in effect dissolve in their own crystal water, and thus react in the solute state. The compounds selected have a high solubility.
A more recent development is the application of catalysts comprising one Group VIII non-noble metal and two Group VIB metals.
Such a catalyst is disclosed, e.g., in JP 09000929, U.S. Pat. Nos. 4,596,785, U.S. 4,820,677, U.S. 3,678,124, U.S. 4,153,578, and non-prepublished international patent application WO 9903578.
The catalyst of JP 09000929, which is a carrier-containing catalyst, is prepared by impregnating an inorganic support with cobalt or nickel as Group VIII non-noble metal and molybdenum and tungsten as Group VIB metals.
CZ 158758 discloses the preparation of two separate precipitates by combining solutions of the various compounds. The first precipitate is prepared by combining solutions of ammonium molybdate and iron (3+) chloride. The second precipitate is prepared by combining solutions of ammonium molybdate and chromium (3+) chloride. The precipitates are washed in excess of distilled water, which is then removed by decantation. The suspensions of the two precipitates are combined, the mixture is filtered, the filter cake is washed with distilled water and dried static in air at room temperature, shaped by extrusion, dried at room temperature, then at elevated temperature and then calcined. The claim explicitly states that Fe2(MoO4)3 and Cr2(MoO4)3 are prepared from solutions of ammonium molybdate and solutions of soluble Fe(3+) and Cr(3+) salts.
The catalyst of U.S. Pat. No. 4,596,785 comprises the disulfides of at least one Group VIII non-noble metal and at least one Group VIB metal. The catalyst of U.S. Pat. No. 4,820,677 is an amorphous sulphide comprising iron as Group VIII non-noble metal and a metal selected from molybdenum, tungsten or mixtures thereof as Group VIB metal, as well as a polydentate ligand such as ethylene diamine. In both references the catalyst is prepared via co-precipitation of water-soluble sources of one Group VIII non-noble metal and two Group VIB metals in the presence of sulfides. The precipitate is isolated, dried, and calcined. All process steps have to be performed in an inert atmosphere, which means that sophisticated techniques are required to carry out this process. Further, due to this co-precipitation technique there are huge amounts of waste water.
It is therefore a further object of the present invention to provide a process which is technically simple and robust and which does not require any handling under an inert atmosphere during the preparation of the catalyst and in which huge amounts of waste water can be avoided.
U.S. Pat. No. 3,678,124 discloses oxidic bulk catalysts to be used in oxidative dehydrogenation of paraffin hydrocarbons. The catalysts are prepared by co-precipitating water-soluble components of the corresponding metals. Again, the co-precipitation technique results in huge amounts of waste water.
The catalyst of U.S. Pat. No. 4,153,578 is a Raney nickel catalyst to be used for the hydrogenation of butyne diol. The catalyst is prepared by contacting Raney nickel optionally containing, e.g., tungsten with a molybdenum component in the presence of water. Molybdenum is adsorbed on the Raney nickel by stirring the resulting suspension at room temperature.
Finally, in non-prepublished international patent application WO 9903578, catalysts are prepared by co-precipitating certain amounts of a nickel, molybdenum, and tungsten source in the absence of sulfides.
The present invention is a process for the hydroprocessing of a hydrocarbon feedstock wherein said feedstock is contacted at hydroprocessing conditions with a catalyst composition which comprises bulk catalyst particles which comprise at least one Group VIII non-noble metal and at least two Group VIB metals. The Group VIII and Group VIB metals comprise from about 50 wt. % to about 100 wt. %, calculated as oxides, of the total weight of the bulk catalyst particles. The metals are present in the catalyst composition in their oxidic and/or sulfidic state. The catalyst composition has an X-ray diffraction pattern in which the characteristic full width at half maximum does not exceed 2.5xc2x0 when the Group VIB metals are molybdenum, tungsten, and, optionally, chromium, or does not exceed 4.0xc2x0 when the Group VIB metals are molybdenum and chromium or tungsten and chromium.
Other embodiments of the present invention encompass further details relating to the above process, all of which are hereinafter disclosed in the following discussion of each of those facets of the invention.